1. Field of the Invention
This invention relates to a disk device that reads/writes information from a disk storage medium by way of a head, and more particularly to a head position control method and disk device that effectively uses the range of motion of an actuator to increase storage capacity.
2. Description of the Related Art
Disk storage devices such as magnetic disk drives and optical disk drives are widely used as storage devices for computers. Increased disk storage capacity is desired for these kinds of disk storage devices, and the storage capacity has been increasing every year.
FIG. 17 is a schematic drawing of a disk storage device for explaining the related art, and FIG. 18 is a drawing explaining the range of motion of the actuator. As shown in FIG. 17, position information is recorded for each track 0T-10000T on the storage disk 90. The position information comprises a track number and a servo pattern.
The head 94 that reads/writes the disk 90 is moved in the radial direction of the disk 90 by the actuator 91. With this movement, the head 94 can be positioned at each of the tracks on the disk 90. This actuator 91 has a specified range of motion. In other words, the range of motion is limited to a range of desirable movement characteristics of the actuator 91. In order to do this, there is an outer stopper 92 and an inner stopper 93 on the actuator 91.
Therefore the head 94 can only move within the range specified by these stoppers 92, 93. On the other hand, FIG. 18 shows the range of motion for heads A, B, C and D by a different actuator. In other words, the distance between the center of the disk and the center of the actuator, and the distance from the center of the actuator to the head differs for each device. The device is designed and adjusted so that this position relationship is the same for each device, however errors occur.
Recently, the track width of disk devices is 1 xcexcm or less, and when there is error of 50 xcexcm, there is an offset of 50 tracks. Moreover, as shown in FIG. 18, the range of motion of the heads differs slightly for each device. In the prior self STW (servo track write) method, the disk device uses its own actuator to read the position information and format each track so this offset had no effect on the storage capacity.
On the other hand, a method is known of installing disks in the disk device for which the position information has been written and the tracks formatted outside the disk device. In this method, the position information is written on the disk by a special servo track writer, so it is possible to write position information at an accurate position even when the track pitch is small.
However, when using this disk in a disk device, it is necessary to consider the difference in the ranges of motion shown in FIG. 18. For example, even in the case of a fixed-disk device, it is possible to use the common area of each range of motion as the data area, such as in the case of a replaceable disk device.
However, in the related art described above, the common area is only part of the range of motion of the actuator, and the area outside of the common area cannot be used as the data area.
The objective of this invention is to provide a head position control method and disk device that effectively uses the range of motion of the actuator to increase storage capacity of the disk.
Another objective of this invention is to provide a head position control method and disk device that increases the storage capacity of the disk by address conversion.
Yet a further objective of this invention is to provide a head position control method and disk device that uses a disk whose tracks are formatted externally, and that effectively uses the range of motion of the actuator to increase storage capacity of the disk.
In order this objective, the head position control method for a disk device of one form of this invention comprises: a step of converting a logical address to a physical track position of the track such that the data area is set inside the writing area of a disk at a position within a restricted range of motion that an actuator is capable of moving the head over the disk; and a step of driving the actuator according to the position information that is read from the track of the disk by the head and according to the physical track position.
The disk device of one form of the invention comprises: a disk which has a plurality of physical tracks; a head for reading data from or writing data to the tracks of the disk; an actuator that moves the head over the disk; and a control unit that controls the position of the head to a physical track on the disk that corresponds to a logical address; wherein the control unit converts a logical address to a physical track position of the disk such that the data area is set inside the writing area of the disk at a position within the restricted range of motion that the actuator is capable of moving the head over the disk, and drives the actuator according to the position information that is read from the track of the disk by the head and according to the physical track position.
In this form of the invention, the entire writing area of the disk is formatted into tracks on which the position information is recorded. Also, in the disk device in which this disk is installed, a data area is set from that area according to the range of motion of its actuator. According to this setting, logical address starting from the higher order is converted to physical address to control the position of the head. Therefore, even in the case where a track-formatted disk is used in the device, it is possible to effectively use the range of motion of each device to increase the storage capacity. Moreover, this can be accomplished more easily by converting the addresses.
Moreover, a head position control method for a disk device of another form of this invention wherein the conversion step comprises: a step of operating the actuator with respect to the disk and measuring the starting position of the data area; and a step of using the starting position to convert the logical address to the physical track position.
In another form of the disk device of this invention, the control unit comprises a memory for storing the starting position of the data area that is obtained by operating the actuator with respect to the disk and measuring the data area; and a conversion unit for converting the logical address to the physical track position by using said starting position.
In this form of the invention, the starting position is measured for conversion, and since this starting position is used for performing conversion to a physical track position, it is possible to reduce the parameters needed for conversion, reduce the increased amount of data in memory and to make conversion more simple. Moreover, since measurement is performed within the device, it is possible to measure the data area accurately.
Furthermore, in the other form of head position control method for a disk device of this invention, the measurement step comprises: a step of measuring the starting positions for a plurality of areas that are divisions of the data area for a plurality of the heads that correspond to different surfaces of the disk; and a step of converting a logical address to a physical track position by using the starting position of a corresponding area of a corresponding said head number.
In another form of disk device of this invention, the head comprises a plurality of heads that correspond to different surfaces of the disk; the memory that stores all of the starting positions of a plurality of areas that are divisions of the data area for the heads; and the control unit that convert a logical address to a physical track position by using the starting position for the corresponding area of a corresponding head number.
This form of the invention corrects any offset that occurs due to assembly error between heads when there is a plurality of heads in one actuator. In this case, when a rotation-type actuator is used, the amount of offset differs between the outer circumference and inner circumference of the disk, so the offset is corrected by dividing the data area into a plurality of areas, and setting a starting position for each area.
In the other form of head position control method for a disk device of this invention, the measurement step comprises: a step of measuring the offset of the starting positions between all of the heads of the plurality of areas; and a step of setting head addresses that correspond to the logical addresses according to the offset of the plurality of areas.
In the other form of disk device of this invention, the memory stores the offset between the heads of the plurality of areas, and stores head addresses that are set to correspond to the logical addresses according to the offset in the plurality of areas.
In this form of the invention, when storing the relative offset for each area, a reference head for the relative position offset is set so that the areas do not overlap. Therefore, by converting the addresses, it is possible to prevent overlapping of areas even when relative offset is used to reduce the memory capacity.